1. Field of the Invention
The present invention relates generally to lifting devices, and more particularly, to a permanently-installed wheelchair lift device with an improved height control mechanism to provide access to stages, platforms, risers and other elevated structures for individuals with disabilities.
2. Description of the Background Art
Under the Americans With Disabilities Act of 1990 (the “ADA”), the U.S. government required that public buildings be accessible to the disabled. For persons requiring a wheelchair for mobility, abrupt changes in floor elevation have to be modified to enable access by wheelchair. The ADA permits vertical lifting devices to be used instead of a ramp.
Lifting devices for the disabled are known in the prior art. For example, U.S. Pat. No. 5,105,915 (Gary) describes a lifting device having a car including fixed sides and short, one-piece ramps at each end. The car is raised and lowered by a pantograph jack including a hydraulic pump driven by an electric motor controlled by switches. The patent also describes several lifting devices of the prior art. Another wheelchair lifting device is disclosed in U.S. Pat. No. 6,182,798 to Brady, et al., and assigned to AGM Container Controls, Inc., the assignee of the present invention. The '798 patent discloses a portable lift device with gates at both ends of the lift car, transparent walls, a loading ramp, a dock plate, a stage height sensor, and numerous safety features. On the other hand, the height detection system disclosed in this patent involves mechanical contact between the lift car and a sensor positioned on the stage.
Another portable lifting device adapted for wheelchairs is disclosed within pending U.S. patent application Ser. No. 11/026,863, filed on Dec. 30, 2004, and published as U.S. Publ. No. 20060182570 (Zuercher, et al.) on Aug. 17, 2006, also assigned to the assignee of the present application. This application discloses a height adjustment mechanism accessible through a panel of the lift car for varying the elevational height of the lift. A rotatable arm is used to set the elevational height, and a knob secured to the end of such rotatable arm slides within a circular slot. The knob can be loosened to move the knob within the circular slot, thereby repositioning the rotatable arm. Once the knob is set to the desired elevational height, the knob is re-tightened, and the access panel is closed.
Portable wheelchair lifting devices generally require that the height to which the lift car is elevated be readily adjustable. Such lift devices are frequently moved from one stage or platform to another, and the elevations of two or more stages or platforms often differ from one another. On the other hand, a permanently-installed wheelchair lift remains permanently at a particular location, and once the height has been properly adjusted for a particular platform or stage, further height adjustments are neither required or recommended. During installation of a permanently-installed wheelchair lift, an installer adjusts the height to which the lift is elevated, and it would be desirable to permit such initial height adjustment to be made quickly and easily. Once the installer has adjusted the lift height, the lift device should be able to raise the platform of the lift device repeatedly, and reliably, to the pre-set height.
Lift devices for the disabled often include an entry gate and an exit gate. The entry gate is opened when the lift platform is fully-lowered to allow a user to enter the lift device prior to elevation, or to exit the lift device just after the platform is lowered. A valuable safety feature incorporated within lift devices for the disabled prevents the entry gate from being unlocked unless the platform is within a few inches of its fully-lowered position. Alternatively, the lift device can be configured to prevent continued elevation of the platform if the entry gate is not fully closed and locked by the time that the platform has been raised more than a few inches off the ground. To provide such safety features, it is necessary to sense that the platform is more than one or two inches above the ground.
In view of the foregoing, it is an object of the present invention to provide a lift device suitable for lifting wheelchair-bound users up to the height of stages, platforms, risers and the like in a safe and reliable manner, and comporting with all applicable ADA requirements.
Another object of the present invention is to provide such a lift device including a height control mechanism that does not require any physical contact between the lift device and the stage (or any objects supported by the stage).
A further object of the present invention is to provide such a lift device including a height control mechanism particularly adapted for a permanently-installed wheelchair lift that remains permanently at a particular location, and which reliably raises the lift platform to the same desired height time after time.
Yet another object of the present invention is to provide such a lift device including a height control mechanism for a permanently-installed lift wherein an installer can adjust the height to which the lift is elevated quickly and easily.
A still further object of the present invention is to provide such a lift device including a height control mechanism which can also be used to detect whether the lift platform is more than one or two inches above the ground.
These and other objects of the present invention will become more apparent to those skilled in the art as the description of the present invention proceeds.